Various optical chemical sensors have been devised in recent years. There is high commercial demand for these sensors. For instance, there is high demand for optical oxygen sensors in the fields of foods and chemicals that are not supposed to be oxidized. There is also heavy demand for oxygen detection in industrial fields such as semiconductors and biology. The optical oxygen sensor disclosed in Patent Document 1 is a first example of prior art related to optical chemical sensors that have been invented so far.
With this prior art, an organic dye compound that receives and emits light is dispersed in an oxygen-permeable polymer. This makes use of the fact that the presence of oxygen reduces the emission brightness, so the oxygen concentration can be detected from a change in the emission brightness. This chemical sensor can be used repeatedly, and has good quantitative sensitivity, so it has been put to use in chemical laboratories.
A second example of prior art that has been widely used in the past is an oxygen sensor that makes use of a chemical substance whose color changes in the presence of oxygen. This sensor is inexpensive and easy to manufacture, and has been used in food packaging and so forth.
Because this second example of oxygen sensor prior art is inexpensive, can be sealed right into a food package. However, it is lacking in terms of quantitative sensitivity, so all that can be evaluated is whether the seal of the package has been broken and there is the risk that the food has been oxidized. Also, because it is used in the above-mentioned applications, it is not expected to be reused, and it is premised on a single use and a one-way chemical change. Also, since it contains organic matter, it cannot be used in high-temperature environments.
In this respect, the first prior art example, as mentioned above, can be used repeatedly and has good quantitative sensitivity, but cannot be used in high-temperature environments because it contains organic matter.